“What's the difference between a snapshot and art…when is a snapshot just a snapshot?” To properly answer these two questions, one must ask a third. What is art?

Webster's (1828 English Dictionary) gives a lengthy and somewhat broad definition (see bottom of page):

Researching the meaning of "art" throughout history will unearth an ongoing debate. Until the 17th century, art referred to any skill or mastery and was not set apart from craft or science. In modern usage after the 17th century, where aesthetic considerations become paramount, the fine arts emerge prominently above other acquired skills in general, such as the decorative arts, and applied arts i.e. graphic design, fashion design etc.. 

The earliest sense of art was broad, roughly equivalent to "skill" or “craft” (in keeping with the old Latin meaning), as associated with words such as "artisan." The specifics of what constitutes art have evolved over time, but general descriptions still refer to an instance of applied imaginative or technical skill. Art has been further defined as a vehicle for expression and communication of emotions and ideas; as a means for exploring and appreciating formal elements for their own sake. Concepts such as creativity and interpretation, are now contemplated in a branch of philosophy known as aesthetics. One can not argue that the nature of art, as philosopher Richard Wollheim states, is "one of the most elusive of the traditional problems of human culture".

Art is something that stimulates an individual's thoughts, emotions, beliefs, or ideas through the senses. Often, if the skill is being used in a common or practical way, such as taking a snapshot at a family event or building a table, folks will consider it a “craft” rather then art. When I hear the word snapshot, I tend to think of a quick, carelessly taken image and appreciate Richard Avedon’s words, as they help to clarify some of my thoughts. "Anything is an art if you do it at a level of an art" (brainyquotes.com)

Several of the images in “The Americans” by Robert Frank, might be regarded as mere snapshots. Take for instance ‘Elevator’ and ‘Trolley.’ They could initially present as snapshots, but they are widely accepted as art. Why? Because these images do stimulate one's thoughts, emotions, a sense of a time and place, etc..

This leads us to the question: how do you draw a distinction between appreciating a masterful work, and simply reading too much into an unworthy image? 

I believe that, just as the appreciation of art is subjective, so is the awareness of stretching too far to apprehend it. Only the creator of the image can determine if our accolades are “too much.” Only they may truly know what intention inspired or what message was hopefully conveyed by a particular work. 

I found a wonderfully, cryptic quote on mental floss.com , by R.G. Collingwood - The Principles of Art (1938) “The making of a work of art - is a strange and risky business in which the maker never knows quite what he is making until he makes it.” Following this thought, an image may be undertaken with the intention of generating a work of art but fall short as a snapshot, tossed aside. Conversely, a photograph captured in the reflex of a quick snapshot might occasionally produce a masterful work of art. There are times that this determination will not be made beforehand, but rather in the face of its audience. 

In conclusion, if art is to be considered a creative, aesthetic expression, by way of communicating a feeling or message - not just an acquired skill - then, if and when, an image evokes deep emotion within the viewer’s senses, the image is art. Keeping this in mind, there will be times when the measure of art is unconcerned with the photographer’s intent, and the status of art is thereby measured by its impact. Snapshots on the other hand, if lacking an emotional thrust, aesthetic value, or the formal qualities of design, while a useful means of creating an external memory, are perhaps more simply measured by their printed dimensions.